[browser][MT] lock_thread: g_assert (thread->longlived->synch_cs)

[pavelsavara]

Error Blob

{
  "ErrorMessage": "",
  "BuildRetry": false,
  "ErrorPattern": "Assertion.*threads.c:517",
  "ExcludeConsoleLog": false
}

Reproduction Steps

Log
Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=569381

[14:59:35] info: [STRT] System.Text.Json.Tests.JsonDocumentTests.ParseJson_UnseekableStream_Async_WithBOM(compactData: False, type: DeepTree, jsonString: "[\n  {\n    \"_id\": \"5af4bfbe93ba383385d9047a\","···)
[14:59:35] fail: [0x2e440000-long 14:59:35.778] [MONO] * Assertion at /__w/1/s/src/mono/mono/metadata/threads.c:517, condition `<disabled>' not met

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=569381
Error message validated: [Assertion.*threads.c:517]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 2/17/2024 12:34:27 PM UTC

Report

Build	Definition	Test	Pull Request
595316	dotnet/runtime	WasmTestOnBrowser-System.Net.WebSockets.Tests.WorkItemExecution	#98986

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	0	1

[ghost]

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Issue Details

---

Error Blob

{
  "ErrorMessage": "",
  "BuildRetry": false,
  "ErrorPattern": "Assertion.*threads.c:517",
  "ExcludeConsoleLog": false
}

Reproduction Steps

Log
Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=569381

[14:59:35] info: [STRT] System.Text.Json.Tests.JsonDocumentTests.ParseJson_UnseekableStream_Async_WithBOM(compactData: False, type: DeepTree, jsonString: "[\n  {\n    \"_id\": \"5af4bfbe93ba383385d9047a\","···)
[14:59:35] fail: [0x2e440000-long 14:59:35.778] [MONO] * Assertion at /__w/1/s/src/mono/mono/metadata/threads.c:517, condition `<disabled>' not met

Author:	pavelsavara
Assignees:	-
Labels:	arch-wasm, blocking-clean-ci, area-VM-threading-mono, Known Build Error, os-browser
Milestone:	9.0.0

[lambdageek]

One idea might be to change init_thread_object from this:

	thread->longlived = g_new0 (MonoLongLivedThreadData, 1);
	init_longlived_thread_data (thread->longlived);

to this

	MonoLongLivedThreadData *lltd = g_new0 (MonoLongLivedThreadData, 1)
	init_longlived_thread_data (lltd);
	thread->longlived = lltd;

because otherwise some thread might see thread->longlived != NULL && thread->longlived->synch_cs == NULL.

With the fixed order, the membarrier inside init_longlived_thread_data will ensure that if thread->longlived != NULL then thread->longlived->synch_cs != NULL.

[pavelsavara]

no more occurrences, please reopen if you see it again